The present invention relates to a scanning probe microscope, semiconductor distortion sensor for use therein and a manufacturing process for manufacture thereof. More particularly, the invention concerns a scanning probe microscope suitable for use as a scanning type inter-atomic force microscope (AFM Atomic Force Microscope), semiconductor distortion sensor for use therein, and a manufacturing process for manufacture thereof. More specifically, the invention concerns a semiconductor distortion sensor in which a pn junction is formed in a flexible portion of a cantilever that has been constructed of a semiconductor substrate to thereby enable the detection of the amount of flexure of the cantilever as a change in the diode characteristic at the pn junction portion, a manufacturing process therefor and a scanning probe microscope that has adopted this semiconductor distortion sensor as the cantilever.
In a conventional scanning type inter-atomic force microscope (AFM), a probe is mounted on the free end of the cantilever, whereby the amount of flexure of the cantilever which is produced when the probe moves up and down in corresponding relation to the irregularities of the sample surface has hitherto been detected using optical interferometries, optical beam deflections techniques, etc. However, these optical detection methods have involved therein the problem that the relevant construction is complex and the relevant adjustment also is difficult. On the other hand, recently, as a sensor for detecting the amount of flexure, acceleration, etc. there has become widely used a semiconductor distortion sensor that has the feature of its being small in size and light in weight and of enabling direct output of the amount of flexure as an electric signal. This semiconductor distortion sensor has come to be adopted also in the cantilever of the AFM.
As illustrated in, in for example, FIG. 13, the conventional cantilever type semiconductor distortion sensor is composed of a cantilever arm portion (beam portion) 1 which has a free end 1a that has been formed by etching selectively a part 2 of a semiconductor substrate into the shape of "a letter U" and a gauge portion 3 that has been formed near a fixed end and its vicinity (the foot) of the cantilever arm portion 1. The gauge portion 3 detects the stress-caused distortion that occurs therein in corresponding relation to the amount of flexure of the free end 1a and outputs it by converting it to an electric signal,
As is described in, for example, Japanese Patent Laid-Open Publication No. 5-196458, in the conventional semiconductor distortion sensor, the gauge portion 3 is constructed of a piezoresistive resistor. Since the piezoresistive resistor has its electrical resistance varied upon application thereto of a stress, the detection of the amount of flexure has hitherto been performed by measuring the change in the resistance of the piezoresistive resistor by a resistance bridge circuit such as a Wheatstone bridge circuit.
As mentioned above, when the amount of flexure of the cantilever attempts to be detected as the stress-caused distortion applied to the piezoresistive resistor, since in the case of the piezoresistive resistor the rate of change in the resistance, in other words, rate of change in the voltage or current, relative to the amount of distortion is low and the measuring sensitivity is low, the detection of the amount of flexure not only requires the use of a complex resistance bridge circuit but also raises the problem that it is necessary to adjust very accurately the respective resistors that constitute the resistor bridge circuit.
The object of the present invention is to provide a semiconductor distortion sensor which solves the above-mentioned problems of the prior art and outputs the amount of flexure of the cantilever as a large change in signal with a simple structure, a manufacturing process therefor and a scanning probe microscope that has adopted this semiconductor distortion sensor as its cantilever.